In the anionic polymerization of lactam, especially E-caprolactam, an anionic polymerization catalyst and an activator (or promoter) are typically present. Various kinds of activators are disclosed in the art.
One proposal for an activated anionic catalytic polymerization process is described in U.S. Pat. No. 3,304,291. The activator used therein consists of organic nitrogen compounds having on at least 2 to 12 carbon hydrocarbon radical being an N-substituted compound of at least one urea, thiourea or guanidine radical.
An improvement thereon for producing polylactams having a higher notch impact strength includes conducting the activated anionic catalyzed lactam polymerization process in the presence of a quantity of a polyether soluble in the molten lactam or the mixture of lactams being polymerized. the polyether is limited to at most about 25% by weight of the quantity of the lactam to be polymerized, otherwise the resultant polylactams possess poor mechanical properties.
An isocyanate promoter having at least one isocyanate compound has been used in an anionic catalytic polymerization of a lactam conducted in the presence of a polyether soluble in molten lactam.
As further described in U.S. Pat. No. 3,704,280, it is required that the absolute number of hydroxyl (OH) groups contained in the polyether is greater than the absolute number of isocyanate groups contained in the isocyanate employed.
Another improved process for the anionic catalytic polaymerization of lactams aided by one or more promoters described in U.S. Pat. No. 3,770,689 includes adding to the reaction mixture one or more polyether compounds having etherified hydroxyl groups which are soluble in the molten lactam or lactam mixture. Conventional promoters suitable for use therein include polymer chains permanently terminated on at least one end by a promoter function. Generally the promoter functional groups or substituents are similar to monomeric promoters such as acid-chloride groups, isocyanates, N-carbonyl-lactam groups, imide groups, N-carbonyl-sulfonamide groups, N-carbonyl-urea groups and acid-anhydride groups.
U.S. Pat. No. 3,987,033 describes a composition prepared by reacting an aromatic diisocyanate with a triprimary alcohol and subsequently reacting this product with a mixture of a hydroxy component such as a phenol.
U.S. Pat. No. 4,171,305 describes pure crystals of E-caprolactam diblocked w,w'-diisocyanato-1,3-dimethylbenzene used as a hardener of powder coating composition.
U.S. Pat. No. 4,211,699 describes isocyanate adduct diols derived from an amino diol or a hydrazine diol and an organic diisocyanate and their use for the production of self-crosslinkable and/or self-crosslinked polyurethanes.
U.S. Pat. No. 3,018,273 describes a process for in situ polymerizing caprolactam in the presence of an organomagnesium initiator compound, and an N,N diacyl promoter compound. Preferably, the N, N diacyl promoter compounds are N-substituted imides, such as cyclic imides of dicarboxylic acids, having molecular weights not exceeding 1000 in order to preclude the presence of large inert groups in the promoters. The molecular weights preferably do not exceed 500.
British Pat. No. 1,067,153 describes a process for preparing nylon-block-copolymers by anionically polymerizing caprolactam in the presence of an isocyanate capped polypropylene glycol and a potassium based catalyst. In this process a nylon block copolymer containing at least one polyether block is formed.
In the U.S. Pat. Nos. 3,862,262, 4,031,164, 4,034,015 and 4,223,112 various aspects of the preparation of nylon block copolymers from caprolactam in the presence of an acyl lactam activator are described. U.S. Pat. No. 3,862,262 describes lactam-polyol-acyl-polylactam block-terpolymers. U.S. Pat. Nos. 4,031,164 and 4,223,112 describe lactam-polyol-polyacyl-lactam-block terpolymers having a specified ratio of the various components. More particularly U.S. Pat. No. 4,031,164 discloses the use of 18 to 90% by weight of polyol blocks in the terploymer. U.S. Pat. No. 4,034,015 is directed to lactam polyol-polyacyllactam or lactam-polyol-acyl-poly-lactam block terpolymers having at least about 5% ester end group termination.
Reissue Pat. No. Re. 30,371 describes the preparation of polyester-polyamide compounds by condensation of an alcohol and an acyl lactam in the presence of at least one of a metal or metal compound, the metal components thereof being selected from Group IA, IIA, IIB and IIIa of the Periodic Table.
Preparation of nylon compositions by anionicaly polymerizing at least 75% lactam with up to about 25% of an epoxy component in the presence of a basic catalyst and promoter is disclosed in U.S. Pat. No. 4,400,490. The promoters are those typically used in the anhydrous polymerization of lactams.
It has been suggested in a paper by Sibal et al, Designing Nylong Polymerization Systems, apparently presented in part at the 2nd International Conference on Reactive Polymer Processing, Pittsburge, Pa. in November 1982. Connection with the anhydrous anionic polymerization of caprolactam to prepare a co-catalyst or initiator by reacting isocyanate with dried caprolactam at 80.degree. C. Initially, the dried caprolactam may be heated and about 20% thereof boiled off with the residue portion being reacted with an isocyanate, the isocyanate being obtained by slowly reacting 1 mole polypropylene glycol (M.W. 2000) with 2 moles hexamethylene diisocyanate. However, it is clear that further work is needed to determine processability of polylactams produced using this promoter.
The published (Dec. 22, 1983) European patent Applications Nos. 67693 and 67694 describe specific lactam compounds based on various kinds of hydroxy compounds. The published (Dec. 22, 1983) European Patent Applications Nos. 67694 and 67695 describe the use of these lactam compounds in the preparation of nylon.
Serious defects of prior experimental nylon block copolymers included relatively high water absorption. That results in lowered mechanical strengths of "RIM" nylon products.
Additional disadvantages associated with prior experimental nylon block copolymers have included relatively long mold retention times, inferior surface appearances, and decreased polymer strengths caused by incorporation of various copolymer blocks. These disadvantages are most manifest in comparison to reaction-injection molded urethanes.